Abstract
In 1909 the authors published a plethysmograph method for determining the rate of blood flow in the arm (Heart, I., 87) The results obtained by this method for normal individuals, partly or completely stripped to the waist, under the ordinary conditions of room temperature, usually lay between 2 and 5 c.c. of blood flow per 100 c.c. of arm substance per minute. More recently, by a calorimeter method, G. N. Stewart has obtained rates in the hand approximately 10 c.c. of blood flow per 100 c.c. of hand substance per minute. We have attempted to compare the two methods because it seemed improbable to us that this discrepancy could depend entirely upon variations in external conditions, such as the room temperatures or the amounts of clothing worn.
The plethysmograph method was applied to the hand and the results compared with those obtained by the calorimeter method on the hand and with those obtained when the plethysmograph included the forearm and the lower arm. Our method does not give very satisfactory results for the hand. The curves are apt to rise abruptly when the pressure is applied and the rate of swelling remains constant but a short time before it lessens, owing apparently to the small venous capacity of the hand.
It is nearly always possible, however, to obtain curves where the rate of inflow is nearly constant for 2 C.C. or more. By selecting such parts of the tracings, an approximate rate of flow in the hand was obtained.
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